The voluntary scheme, introduced by the Department of Health in 2013, sees foods highlighted as red, amber or green according to how much salt, sugar and fat they contain.
But the labels do not appear on about a third of the food sold in the UK.
The Local Government Association (LGA) said current rules were confusing and a universal labelling system was needed.
It said with obesity levels rising, clearer packaging would help people take more responsibility for their health.
Izzi Seccombe, chairwoman of the LGA’s community wellbeing board, said many retailers and manufacturers had different methods of displaying nutritional content.
“Consumers need a single, standard and consistent system which should be universally adopted. It needs to be something that they can read and understand quickly and easily,” she said.
“The UK is leading the way with its traffic light scheme, which is already widely used, and provides clear, at-a-glance information. It is something many shoppers are familiar with and find helpful.
“But we want the government to go one step further and make it mandatory for all retailers and manufacturers to adopt.”
Under its recently announced childhood obesity plan, the government said it would look again at how nutritional information was displayed.
The plan was attacked as “weak” by health experts, campaigners and MPswho said the government had “rowed back” on earlier promises.